Electro-magnet lift magnets like those installed on cranes have through the years used a DC generator, rheostat, electric controller and a lift-drop switch. Direct current generators many times are a mechanical and electrical with commutators and specific rotation requirements having contributed to all kinds of maintenance problems. The controllers for such systems are big, heavy and strong requiring very large contacts and high voltage insulation all contributing to high component costs. In a sense the controller is the heart of such systems with the magnet controlled to lift magnetic material and then drop the material lifted in accord with a controller switch position. These controllers are electrical and mechanical devices designed to go "ON" and later "OFF". For example, when the controller switch is activated to the "ON" state heavy lift contacts through approximately one second press together with spring action to pass 240 volts at 50 amps through to the coils of the magnet for the magnet to be in the lift state. Then when the crane magnet has been moved to a drop position the operator puts the controller switch in the "DROP" position. This opens up the "LIFT" switch contacts and then-approximately one second later the lower rated "DROP" contacts close reversing the current through the pre-set time. At this most important critical moment of control when "DROP" starts after the "LIFT" contact is open there is a 30,000-50,000 volt arc fire. This is a critical amount of current to absorb with it important that the design of the control be such as to absorb the high voltage current in the order of 75% or more depending on the brand of control and magnet. The other approximate 25% goes to the magnet coils and magnetic field wise to magnet material. If the control does not reduce the voltage arc voltage current percentages 25-40% may go to the magnet. So in addition to heavy duty relay switch contact burn out you see magnet coils at ground., or in short, or open. With magnet costs of $10,000.00 plus repair costs of approximately $6,000.00 in such condition you have some $15,000.00-$16,000.00 invested. Further, high cost controllers designed to synchronize time with the induction factors of the magnet to reduce high voltage sparking require maintenance and repair by very special technicians. There ave not too many electricians working with generators, controllers and magnets who understand exactly what happens interplay wise when DC, inductivity and time factors all interplay in the same short time span.
Use of an alternator as a power source for an electro-magnet along with a new control system result in great advantages over the presently existing and pre-existing DC powered systems, and control with DC generator, for electro-magnets. First, an alternator has low maintenance, no commutator, no brushes, no high voltage excitation, no specific direction of rotation and no special personal attention in operation. Additionally, the control in such a lift magnet system, advantageously, over a conventional control, is lighter, quieter, low in noise, sparking reduced to a minimum if any, no high voltage and with switch contactors useable for millions of times. With a mercury displacement relay switch there is a low predictable contact resistance in a switch capable of handling a variety of loads with assured consistent switching. The switch is moisture resistant and employs high dieelectic value materials. There is a great reduction in maintenance costs along with increased equipment utilization by reduced downtime and high productivity. Personal attention is greatly reduced and both operational and maintenance costs are reduced.